As I understand it, there is no advantage at present time. 6.5 Grendel was patented by AA, which limited who could produce barrels chambered in the caliber. The workaround for barrel makers who didn't want to honor the patent, was to come up with minimal changes to the chamber dimensions and coin it a different name, like .264LBC or whatever. In this way, they could ream Grendel compatible barrels, without risking lawsuits from AA, because its technically not a "Grendel." Now that SAAMI has adopted the 6.5 Grendel, its a moot point. I don't believe you will really gain or lose anything with variant chambers. Accuracy will be a function or barrel maker and quality. Buy what you can afford. I have a Satern 6.5 Grendel, and it shoots 0.5 MOA. I've heard you can buy economical and accurate barrels, which all seem to really be expensive compared to 5.56, but if buying some of the discount brands, you're going to be rolling the dice and will likely end up negating the inherent accuracy of the cartridge and thus not be impressed.

Actually, the only requirement that Bill A had for anyone who wanted to use the 6.5 Grendel name was that they had to sctrictly adhere to his chamber specs. Those that wanted to change the chamber (for whatever reason) couldn't use the name. Since SAAMI approved the 6.5 Grendel, that is now the "official" spec and all trademarks have been released. Anyone who wants to make one can now make one.

The 6.5 CSS, .264 LBC, 6.5 Sporter and 6.5 SAOD all have slightly different neck dimensions and throat angles than the actual 6.5 Grendel design. While the other chambers will shoot the factory 6.5 Grendel ammo, there is a rumor that they might have problems with the forthcoming steel-cased stuff from Wolf. On the flipside, the tighter necks have been rumored to be a bit more accurate than the Grendel proper.

I have two 6.5 Grendel barrels (18" and 24") directly from AA, and a third (18") is on the way from AR15Performance (with a .264 LBC chamber) now, so I'll see for myself before long.

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I'm not sure how the chamber variants could be much more accurate than the Grendel chamber.

I shoot sub .25 MOA groups with my Grendel rifles, and others do the same.

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The Grendel chamber is designed to allow the use of multiple different bullet profiles and still have all of them perform accurately. It seems to do that, with my rifles shooting essentially every bullet I've tried at less than 1.5 MOA, and most under 1 MOA, including the different factory ammos.

With a SAAMI spec for the cartridge and chamber, there is little reason to get any other.

What do you say when you have a variant chamber and are shooting ammunition marked "Grendel" and the gun blows up? Who's taking responsibility for that? Since LBC does make a load for their chamber, I would stick to their ammunition if I went that route. None of the others make ammunition, so regardless of whether you use Grendel or LBC ammo, you are not shooting it in the chamber for which it was designed.

Of course, if all you shoot is your own loads, you're on your own anyways!